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Plasma-sprayed hydroxyapatite (HA) coatings with flame-spheroidized feedstock: microstructure and mechanical
1School of Mechanical & Production Engineering, Nanyang Technological University, Singapore, Singapore.
Biomaterials
|May 16, 2000
Summary
Optimizing plasma-sprayed hydroxyapatite (HA) coatings involves controlling feedstock particle size and spray distance. Best mechanical properties were achieved with smaller HA particles and shorter spray distances, with heat treatment at 800°C further enhancing performance.
Area of Science:
- Biomaterials Science
- Materials Engineering
- Surface Science
Background:
- Hydroxyapatite (HA) coatings are crucial for biomedical implants due to their biocompatibility.
- Plasma spraying is a common technique for applying HA coatings, but properties are sensitive to processing parameters.
- Understanding the relationship between feedstock, processing, microstructure, and mechanical properties is vital for optimizing HA coatings.
Purpose of the Study:
- To investigate the influence of feedstock characteristics and plasma spraying parameters on the mechanical properties and structural integrity of hydroxyapatite (HA) coatings.
- To correlate microstructural defects with the resultant mechanical performance of the coatings.
- To evaluate the effect of post-deposition heat treatment on the properties of HA coatings.
Main Methods:
- Flame-spheroidized hydroxyapatite (HA) feedstock with varying particle sizes (20-45, 45-75, 75-125 microm) was used for plasma spraying.
- Processing parameters, including spray distance (10, 12, 14 cm), were systematically varied.
- Mechanical properties (microhardness, modulus, fracture toughness, bond strength) and microstructural features (cracks, voids, porosity) were analyzed.
- Heat treatment was performed at 600, 800, and 900 degrees C.
Main Results:
- Increased HA particle size and spray distance led to decreased mechanical properties and structural stability.
- Microstructural defects such as thermal microcracks, voids, and limited lamellar contact degraded coating characteristics.
- Heat treatment at 800 degrees C significantly enhanced microhardness and elastic modulus (P < 0.05).
- Coatings produced from 20-45 microm HA feedstock sprayed at 10 cm exhibited the most favorable mechanical properties.
Conclusions:
- The mechanical properties and structural integrity of plasma-sprayed HA coatings are strongly dependent on feedstock particle size and spray parameters.
- Optimized processing conditions, specifically using smaller HA particles and shorter spray distances, yield superior coatings.
- Post-deposition heat treatment at 800 degrees C is beneficial for improving the mechanical performance of HA coatings.